Can you be more descriptive in your question
The correct answer would be the second option. The correct plan for his experiment would be that the temperature, the type of limestone, and the type of acid are controls. The amount of acid and the amount of damage to the limestone are variables. To determine the degree of damage of the acid it would be best that the amount of acid is the manipulated variable while everything else are assumed constant.
You are correct. The first statement that you had was the right answer.
Answer:
Remember that the unemployed are those who are out of work and who are actively looking for a job. We can calculate the unemployment rate by dividing the number of unemployed people by the total number in the labor force, then multiplying by 100.
Explanation: